Generally, magnetic components use magnetic materials for shaping and directing magnetic fields in a manner designed to achieve a desired electrical performance. Magnetic components are readily used in a wide variety of electronic equipment such as computers, televisions, telephones, etc. In operation, magnetic fields may act as the medium for storing, transferring, and releasing electromagnetic energy. Transformers are one specific example of a magnetic component, and typically comprise two or more windings of conductors (e.g., copper wire) wound around a bobbin with a magnetic core inserted through the bobbin. The bobbin may generally be made of a molded plastic or any other suitable dielectric material. The conductors may be wound around the bobbin a predetermined number of times and in a predetermined configuration to achieve specific electrical characteristics. For example, the number of windings (e.g., a primary winding and a secondary winding) and the number of turns for the conductors in each winding may be a function of the intended application for the transformer.
To form the magnetic field in the transformer, a core assembly having high magnetic permeability may be inserted into the bobbin. Often the core assembly is made in two pieces, each having an “E” shaped cross-section that may be inserted into opposite ends of the bobbin. The transformer assembly may then be held together by various physical means such as a spring clip, tape, or an adhesive.
Transformers generally operate on the principle that a change in current flowing through a first winding conductor, which is isolated from a second winding conductor, creates a magnetic flux that causes a change in the current flow in the second winding conductor. The ratio of current in the two winding conductors may generally be related to the relative number of windings of each conductor. This may in turn create a voltage that may be the product of the number of turns multiplied by the change in magnetic flux.
As electronic manufacturers are constantly striving to develop components that are smaller and less expensive, there is a need for magnetic components that meet these requirements. Constricting the size of magnetic components presents unique design challenges, as the devices must still accommodate special features that are required by the manufacturability and electrical performance characteristics of a particular application. In space-constrained applications that require magnetic components to be small in height and capable of being mounted on a printed circuit board (PCB), planar type magnetic devices (e.g., planar transformers) may be used. Planar transformers are typically made using copper lead frames and flat copper spirals instead of copper wire wound around ferrite cores as described above. The spirals may be etched on thin sheets of dielectric material and stacked on flat ferrite cores to form the magnetic circuit. Although planar transformers are useful in that they can be relatively small in size, they have a number of drawbacks (e.g., cost, efficiency, current carrying ability, etc.) that make it desirable to have alternative designs available. It is against this background that the planar core structure described herein has been developed.